The present invention relates to a new and improved method for fabricating precision teeth and to an apparatus for the performance of such method.
Generally speaking, the method of the invention serves for fabricating precision teeth with at least one free tooth end, wherein there is initially produced a workpiece with approximately shaped teeth, which are then finished rolled in a separate working cycle by cold forming or working.
The apparatus for the performance of the inventive method comprises a machine frame, at least one rolling head carriage mounted therein and displaceable with a linear crosswise or transverse motion with respect to the workpiece. In the rolling head carriage there is mounted a revolvingly drivable rolling head at which there is rotatably mounted at least one roll. This apparatus further comprises a workpiece holding device which is drivable in the lengthwise and rotational direction with respect to the feed or advance of the workpiece. There also is provided a drive synchronization for synchronizing the rolling head drive with the workpiece feed or advance, and a hydraulic drive for feeding or advancing the rolling head carriage towards the workpiece up to a stop and back into a rest position.
As a preliminary observation it should be mentioned that precision teeth can be produced by cold rolling from the solid material according to the known method of the assignee of this application, as disclosed, for instance, in German Pat. No. 1,016,222. These precision teeth do not require any post treatment of the type described in the present disclosure.
With teeth produced in a different manner, whether such be by cutting or non-cutting machining cycles, it is necessary to carry out post-treatments by cutting or non-cutting methods, for instance, by substantially gear-shaped tools, in order to achieve high precision and good surface quality. During the generating of the workpiece material can be shifted or repositioned towards the pitch circle, on the running-in flank, and away from the pitch circle, on the running out flank, thus leading to an asymmetry. Both in the case of machining in a cutting manner with substantially gear-shaped tools meshing with the teeth, as by abrading or scraping, or in a non-cutting manner, as with finish generating, the tools tend to follow the inaccuracies of the teeth so that their corrective effect is not sufficient. The fabrication of such tools is very expensive and requires many tests for determining their shape or form. Furthermore, it is possible that the surface of the approximately shaped teeth, for instance, when manufacturing the approximately shaped teeth by broaching, is such that such cannot be worked by scraping or finish generating but have to be ground.